Regarding a motor having an armature core and a permanent magnet, it is required that a magnetic flux from the permanent magnet is effectively utilized with a simple configuration. In order to satisfy this requirement, JP-2008-35639A (US-2008/0024026A1) proposes a motor having a soft magnetic material between an armature core and a permanent magnet. The soft magnetic material, which is referred to as a magnetism guiding portion, is disposed on an inner surface of the permanent magnet. Thereby, the magnetic flux from a permanent magnet flows through the soft magnetic material and is introduced into the armature core.
Generally, in a motor, an axial length of a permanent magnet is longer than that of an armature core. Thus, the magnetic flux generated from a portion of the permanent magnet located outside of the armature core is likely more reduced than the magnetic flux generated from the other portion of the permanent magnet. Meanwhile, in the motor disclosed in JP-2008-35639A (US-2008/0024026A1), since the soft magnetic material is fixed on the permanent magnet, the magnetic flux can be appropriately introduced into the armature core even if generated from a portion of the permanent magnet located outside of the armature core. FIG. 50 is a chart showing a magnetic flux flowing through the soft magnetic material.
In order to miniaturize a motor, the pole number of a motor is increased. That is, a plurality of permanent magnets is arranged along a rotation direction of the motor in such a manner that N-pole magnetic regions and S-pole magnetic regions are alternately positioned. As shown in FIG. 51, the soft magnetic material (magnetism guiding portion) is provided to each of the magnetic regions, whereby the magnetic flux easily flows into the armature core through the corresponding soft magnetic material. As a result, even if a plurality of permanent magnets is provided, the magnetic flux from the permanent magnets is effectively utilized.
However, in a case that the soft magnetic material (magnetism guiding portion) is provided to every permanent magnet, the number of the soft magnetic material is increased. As a result, the number of parts of the motor is increased and manufacturing step of the motor is also increased.